1. Lesson 2-8
Proof Review

2. Objectives
Write proofs

3. Vocabulary
No new vocabulary

4. Given: 4x – 14 = 2x + 16 Prove: x = 15 Statement Reason
Geometric Proof Worksheet
Given: 4x – 14 = 2x + 16
Prove: x = 15
Statement
Reason
4x – 14 = 2x + 16
Given
x = 15
Substitution

5. Definition of Congruence
Given: AD  BE
Prove: AB  DE A B C D E
Statement
Reason
AD  BE
Given
Definition of Congruence
AD = AB + BD
BE = BD + DE
AB + BD = BD + DE
Substitution (lines 3 & 4 into 2)
Subtraction
AB = DE
Substitution
AB  DE

6. Given: 2 is complimentary to 1 3 is complimentary to 4 2  4
Prove: 1  3 4 2 3 1
Statement
Reason
2  4
Given
2 is complimentary to 1
3 is complimentary to 4
Substitution (1 into 3)
1  3

7. Given: Two intersecting lines Prove: 1  32 1 3 4
(i.e., Prove the Vertical Angle Theorem!)
Statement
Reason
Two intersecting lines
Given
1  3

8. Summary & Homework Summary: Homework: study for Quiz
Proofs are a step-by-step deductive reasoning approach to problem solving using definitions, theorems, postulates and givens.
Homework: study for Quiz